Telephone-repeater



i. MILLS. TELEPHONE REPEATER APPLICATION FILED IAN. I5, I9II.

Patented Sept. 7, i920.,

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J. MILLS. TELEPHONE REPETER. APPLICATIQN FILED 1AH.15,1917.

Patented Sept. 7, LSZ.

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JQHN' IVHLLSOF WYOMNG, NEW JERSEY, ASSIGNOB TO .AMERICAN TELEPHONE .AND TELEGRAPI-l COMBANY, A. CGRPORATGN GF NEARY Ytl..

ELEPHNEeREPEeTER.

assises.

Specication of Letters atent.

Patented Sent. T, i920.

To all whom it may conce/m.'

Be lit known that l, Jorrit Mints, residing at 1Wyoming7 in the county of Essex and State of New Jersey, have invented certain improvements in 'lelephone-Repeaters7 ot which the following is -a specification.l

This invention relates to telephone repeater circuits and more particularly to two- Way, two-repeater circuits associated With convenience composited telephone and telegraph lines. Its object is to reduce and substantially eliminate the tendency 'of the repeater to sing. This result is accomplished by constructing an artificial line or balancing net- Work for the repeater which not only siinulates the characteristics of the telephone circuit,'but also simulates the characteristics of the composite and other auxiliary appau ratus associated With said circuit.

The invention may be understood by reiference to the accompanying drawing in which Figures 1 and 2 constitute diagrams of two circuit arrangements in which .the invention may be embodied.

Referring to Fig. 1, L1 is an incoming composited line working through a transformer 1l into a circuit 2 across which is bridged the primary ot a transformer 8 whereby telephone currents incoming over line L1 are impressed upon the input circuit t ot a repeater element 5, herein shown Jfor as a mechanical repeater although it may in practice be a vacuum tube or other type ot repeater. The output circuit 6 or" the repeater 5 Works through a transformer Z into a circuit `8 similar to circuit 2. The amplified energy in output circuit 6 when impressed upon circuit 8 tends to divide, one-halt Working through a transformer 9 into an outgoing line L2, and the other hall2 Working through transformer 9' into a balancing artificial line orl net-Work llc. The primary of an induction coil 11 is bridged across circuit 8 in such manner that its terminals arev at equal potential with respect to' out-put energy from repeater 5, so that no energy ivorlrsbaclr through input circuit 12 to repeater 13. Energy incoming over line L however, affects transformer .11 and is transmitted over input circuit 12 `to repeater 13 Where it is amplified in output circuit 141 and impressed upon circuit 2 through transformer 15. rlhe energy in 'this circuit divides, one-half going to line L1 to simulate the characteristics of lines L1 and L2 in manner well known in the art. Where, as in the present case, the lines are composited and phantoined, provision must be made to balance the composite phantom apparatus.

ln the arrangement shown the tivo conductors of each line are used to transmit telegraphic signals thereby necessitating the provision of certain auxiliary apparatus. For this purpose conductors 17 and 18 are led to Morse sets from the line conductors through impedance coils 19 and 2O adapted to prevent the passage of telephoneA currents. Any telephone currents which may passv the impedance coils are shunted to ground through condensers 21 and 22 which are opaque to telegraph currents. Condensers 28 and 2li are inserted in the line to prevent the passage of Morse currents to the repeater, but readily permit the llow of telephone currents to the transformer 1. Any telegraph impulses Which pass through the condensers 23 and 24 are shunted .to ground through circuits containing inductances 25 and 26 and capacities 27 and 28 respectively.

ln order to balance the auxiliary appa- .ratus thus associated with the telephone reductors ot a talking circuit as one side ot a phantom circuit thereby necessitating still further auxiliary' apparatus. This arrangement is illustratedin the diagram Where 1' n L c ,Lp t Y in J1 .f unes il an 3 form are aceras ci ne talking circuit ot the phantom .une 115 while the lines L and la. 'orin Jhantorn line L..

n 2 a l n u This result is achieved by connecnng ccnductors 29 and 30 to the mid-points ci' the In this figure inductance coils 25 and rimary windings of induction coil l of line and the corresponding coil of line L3, said conductors being associated with the input circuit of a repeater 31 by a transformer arrangement in all respects similar to that of repeater 5. Similarly a repeater 82 is associated with conductors `33 and 34 leading to the mid-points of primary windings of induction coil 9 of line L2 and the corresponding coil of line L1. Phantom lines L5 and LG are balanced by artificial lines or networks N 5 and N6. Provision must also be made in this case for balancing' the composite apparatus. Accordingly a conductor 29" (corresponding to conductor 29 of line L5) leads to a resistance corresponding to the ohmic resistance of the primary windings of induction coil l, and in parallel through condensers 27, 28 and impedance coils 25, 26 to ground, these elements corresponding to the elements of line L1 having the same reference characters without the double primes. A similar bridge corresponding to the elements of line L3 leads to ground from conductor 30". The resistance may be omitted without appreciably affecting the balance as the induction coil l of line L1 and the corresponding coil 'of line L3 are of almost negligibleresistance.

In order to balance the remainder of the composite apparatus a `condenser 23 having a capacity equal to that of condensers 23 and 24 is inserted in conductor 29 and a similar condenser in conductor 30". A double bridge including impedance coil 19 and condenser 2l in parallel with impedanee coil 20 and condenser 22" is led to ground, the several elements bearing the same relation to each other as the corresponding elements of line L1. A similar bridge leads from conductor 30 to ground. The composite apparatus of the line is now duplicated in the net-work, but it is at once apparent that the ground connection may be omitted without affecting the balance and it is accordingly shown in dotted lines.

By the arrangement above described the composited lines are balancedvby duplicating the essential elements of the composite set in the net-work. However, as it is only necessary to balance the self impedances, any arrangement giving equivalent self impedance will be satisfactory. The arrangement may therefore be somewhat simplified by using the construction illustrated in Fig. 2 in which identical parts are indicated by the same reference characters as in Fig. 1f.

26 o Fig. 1 have been combined in a single inductance 33, while condensers 27 and 28 are combined as one condenser 34. So also impedance coils 19 and 20 appear as one impedance coil 35, condensers 21 and 22 being likewise combined as. condenser 36. Condensers 23 and 24 may also be combined to form ay single condenser 37 in series with one artificial line conductor.

In a similar manner the phantom balancing apparatus may be combined, the four impedance coils of the shunt at the left of condenser-'23 being combined in a single coil 38, the four capacities being likewise replaced bya single capacity 39. Capacity 23 and the corresponding capacity of the conductor 30 arevcombined in a single capacity 40. Finally the double bridge at the right of capacity 23 may be simplified into a single bridge including an inductance 4l 'and capacity 42. It will be clear upon consideration that this simplified arrangement of Fig. 2 will obtain a balance so far as self impedance is concerned although quite simple in form.

While the Ainvention has been disclosed as embodied in a certain specific arrangement it will be understood that it is capable of embodiment in a wide variety of modifications without departing from the spirit of the appended claims:

What is claimed is:

1 l. In a signaling system, two transmission line sections, two artificial lines individually associated with said line sections, translating apparatus, means to associate said translating apparatus with said transmission lines and said artificial lines, auxiliary apparatus associated with a line section and means electrically equivalent to said auxiliary apparatus similarly associated with the corresponding artificial line in order to balance the auxiliary apparatus with respect to the translating apparatus.

2. In a signaling system, two transmission line sections, two artificial lines individually associated with said line sections, translating apparatus, means to associate said translating apparatus with said transmission lines and said artificial lines, auxiliary apparatus associated with a line section and means associated with the corresponding artificial 'line to simulate the characteristics of said auxiliary apparatus. Y

3. A repeater system comprising a transmission line, a repeater, a balancing artificial line for balancing the transmission line with respect to the repeater, means to connect said repeater with said transmission line and artificial line, auxiliary apparatus associated with said line and means associated with the artificial line to simulateethe characteristics of said auxiliary apparatus.

4. A- repeater system comprising a telephone line, an artificial line to balance said telephone line, signaling equipment associated with said telephone line and means associated with the artificial line to simulate the characteristics vof said signaling equipment.

5. A repeater system comprising a telephone line, a repeater, an artificial line to baiance seid telephone line, impedance eleivo equivalent impedance elements in shunt of seid ertiiicial line.

6. A repeater system comprising a telehone line, a repeater, an artiiciul line to balance seid telephone line, ground. tafps connected to each side of said telephone circuit and each including an indnctance and. a capacity and means associated with the artiieiel line for balancing the ground taps comprising an inductance and capacity in shunt of said artificial line.

JOHN MLLS.

lVitnesses M. L. METCALFE, RALPH W. 'Wonn 

